Looking Up: Cygnus the Swan is flying west

Peter Becker More Content Now

Friday

Sep 13, 2019 at 9:21 AM

Fall is coming and along with it you can expect to see geese flying south. How about a celestial swan flying west?

Cygnus the Swan is straight up at around 9 p.m. in mid-September, as seen from mid-northern latitudes. This beautiful constellation, which also contains the starry asterism of the Northern Cross, is patterned with the head of the swan look straight forward as the Swan flies across the sky.

Full Moon was on Sept. 13; it will be rising later and later this week heading toward last quarter on Sept. 21. Even if the sky is moonlit, the main stars of the Swan are visible; by week’s end you will have plenty of chance to see the Swan in all its glory before moonrise.

The unmistakable cross shape make up the principal stars of Cygnus the Swan. To picture it as the Swan, what would be the foot of the cross is the star asking the bird’s head. This star is known as Albireo and it is a magnificent double star. A small telescope magnifying 20x or more will split the pair; one star appears golden yellow, and the other, fainter star, blue. Albireo is about 400 light years away.

The top star of the cross shape is also pictured as the Swan’s tail. This is the brightest star in Cygnus, known as Deneb. This star about magnitude +1.2 and is quite distant: 3,200 light years from the Sun.

The star in the very center of the cross is known as Sadr. From Sadr extend the imaginary lines to the two stars marking either the tips of the cross beam, or the wings of the Swan.

Survey by the Kepler satellite has revealed about a hundred stars in Cygnus with known planets, the most of any constellation.

A nova could appear anywhere in the sky; I’ll never forget the bright nova that appeared in Cygnus in August 1975. It was similar in brightness (magnitude +1.7 at its peak) to other stars in the Cross shape. The “new star” however, altered the constellation for days before it faded away! A nova appears as a dramatic brightening of a white dwarf star which has absorbed gas from a nearby companion star.

As the sky rotates (it’s actually the Earth that is rotating), stars rise in the east and set in the west. The Northern Cross appears to rise in the northeast on its side; when situated due south, the Cross is not straight up and down but tilted to the left. As it sets in the northwest, the Cross appears straight.

To the upper right of this constellation is the small pattern of Lyra the Harp, with its gloriously bright star Vega. To the lower right of the star Albireo is the bright star Altair, in the constellation Aquilia the Eagle. As the Eagle pattern is often pictured, by the way, the Eagle seems to be flying tail first across the sky, contrary to its neighbor the Swan!

From a reasonably dark site, without any moon, you can witness the majestic Milky Way Band extending across the sky on a mid-September evening. Cygnus the Swan straddles the Milky Way. This is a particularly rich area to explore with binoculars or a telescope. There is such a multitude of faint, distant stars packed close together in the Milky Way, it can appear in the telescope eyepiece like a gleaming treasure chest or a static image of millions of snowflakes falling in a winter storm.

In addition, with a detailed star map or atlas you can find your way to a host of star clusters, colored stars, double stars, variable stars and interesting nebulae - both lit and dark like a silhouette against the background stars. Nebulae are vast clouds of gas and dust, spread across the galaxy. They come in various forms.

One particularly fascinating nebula sparks our imagination since it is has a striking resemblance to the continent of North America. Yes, it’s just like children imagining shapes in the puffy clouds on a sunny day, but our star patterns and nebula names help inspire us to keep coming back and to.

Keep looking up!Peter Becker is Managing Editor at The News Eagle in Hawley, PA. Notes are welcome at news@neagle.com. Please mention in what newspaper or web site you read this column.

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